This invention relates to radial tires for automobiles which are excellent from the standpoints of steering stability, riding comfort and durability for use at a high speed.
The development of a freeway network and the improvement in performance of automobiles have given rise to a variety of continuously changing demands for tires of higher performance. For example, there have been a demand for HR tires which are more suitable for use at a high speed than SR tires, or a demand for VR tires which are still more suitable for use at a high speed, and a demand for flat tires which provide a higher degree of steering stability. On the other hand, certain limitations imposed by the tire housings which are available in automobiles have made it desirable to develop tires having a ratio of flattening equal to that of the conventional tires, and which are suitable for use at a high speed and provide a high degree of steering stability.
In order to satisfy these requirements, the tire manufacturers have proposed the use of a bead reinforcing layer which comprises a reinforcing sheet of organic fiber cords. In so far as this reinforcing sheet is composed of substantially the same material as the conventional carcass, however, it has been found unsatisfactory for the reinforcing purpose and incapable of satisfying the requirement for tires having a ratio of flattening equal to that of the conventional tires, and which are suitable for use at a high speed and provide a high degree of steering stability.
After their unsuccessful attempts, they have proposed the use of a bead reinforcing sheet of steel cords. Although the reinforcing sheets of steel cords have been found effective for improving tires from the standpoints of durability for use at a high speed and steering stability, a further improvement has been found necessary from the standpoint of riding comfort, as the high rigidity of steel cords lower the riding comfort to an unendurable extent.